The present invention relates to a proximity switch operable on a non-contact basis and includes a direct current circuit arrangement disposed between and input part and a sensor field producer which is divided into the terminal-side main part, set in a base housing, and a sensor part set in a probe, wherein the probe, for the purpose of selecting the direction of response, can be selectively set in different predetermined positions on the basic housing of the main part.
Non-contact proximity switches serve to trigger electrical switching operations when ever an object spatially approaches or moves away from the switching arrangement. In switches of the aforementioned type, it is principally the modifications, brought about by the approach of the electrically and/or magnetically conductive objects of electromagnetic fields for triggering the switching operations, that have been proposed. In a frequently utilized type of proximity switch, an oscillatory circuit is set into vibration or pulsation by an oscillator. The oscillation is influenced by an approach of electrically conductive objects toward the oscillatory circuit coil or toward a special coil maintained on course by the oscillator whereby, for example, the amplitude of the oscillation is changed by the resistance or the oscillation is entirely interrupted. An evaluation stage connected at the outlet side to the oscillator plots the status of oscillation and, by way of a controller notch, constructs a switching phase of the proximity switch. The output of the switching phase can thereby include contact control such as, for example, a closing of a switch, an opening of a switch, a reversing of a switch, or, in a defined semiconductor phase, such as, for example, a blocked or switched-through phase of a transistor, thyristor or triac, or in a defined signal level. In so-called dual wire proximity switches, the circuit conditions are determined in accordance with certain value ranges of current consumption by the proximity switches.
In all types of inductively operated proximity switches, the coil arrangement such as, for example, a sensor is provided wherein changes in the field are determined in order to form a switching phase. The geometric arrangement of the coils and associated magnetic circuit represents a decisive factor for any alterations of the proximity phase addressed by the proximity switch, that is, in particular from which direction the approach has to occur and the ranges for the change in switching phases.
In a similar manner, other inductively-operating proximity switches such as, for example, optical or capacitive operated proximity switches have also been proposed which include a special sensor arrangement the construction of which determines response direction and the value of the response.
The arrangement of a sensor is of particular importance for the practical application of proximity switches because, in addition to machines, there are often cramped space conditions to deal with which make it difficult for an addition of proximity switches in the required response direction. For this reason, a number of proposals have been made which are often differentiated only by a special arrangement of the sensor such as, for example, a proximity switch having a construction form which is otherwise identical to other proximity switches but being mounted on a front surface or on one of four lateral surfaces.
In, for example, German Pat. No. 2,817,020, to reduce the number of elements necessary to house the sensor arrangement, a square of tube-shaped body is mounted so as to be pivotable on a square or cyliner-shaped main piece or is mounted so that it is capable of being threaded on or plugged into or inserted in various positions. In this manner, the necessary electrical connections between the main piece and the senor part of the proximity switch can be established either by correspondingly movable electric leads or by plug contacts or loop contacts.
A disadvantage of the provision of movable electrical leads in resides in the fact that replacement of the sensor part is difficult because the electrical connections such as, for example, either solder or screw junctions, must be loosened. However, it is desireable to provide for an easy replacement whereby it is possible for the sensor part or parts to be replaced by sensor parts with different response values or response times or by sensor parts having a different principle function when a replacement is necessary due to, for example, mechanical damage. In the event of frequent changing of the response direction by, for example, twisting or turning the sensor part, a fatigue or breakage of the movable leads and their contact points can readily occur.
Employing plug or loop contacts, the construction is, as a rule, somewhat expensive and it is particularly difficult in previously proposed constructions to establish a satisfactory caulking for the connection points that will seal out contaminants such as dirt and liquids. Moreover, the contact points tend to oxidate and corrode thereby lowering the reliability of the proposed plug or loop contact arrangements.
The aim underlying the present invention essentially resides in providing a proximity switch which includes a sensor part which is readily movable and replaceable in a simple and convenient manner.
According to advantageous features of the present invention, a proximity switch is provided wherein a probe thereof is insulated on all sides and a part of the sensor switch as a direct current/alternating current transformer with a follow-on core coil, and with the sensor part having an alternating current/direct current transformer with an aligned core coil. The core coils lie behind each of the fastening sides of a base housing and the probe and, when the probe is released, the energy is release transferred by an inductive coupling from the main part to the sensor part and the signals from the sensor part to the main part.
By virtue of the above noted features of the present invention, it is possible to avoid the disadvantages and problems encountered in the prior art which result from an electrical connection of the main part and the probe. In this connection, even in the probe there is a direct current supply so that the circuit, with respect to an evaluation accuracy, degree of amplification, etc., can be appropriately set up.
In accordance with the present invention, the probe may have a cube-shape and include a fastening side disposed adjacent to a response side and a fastening side disposed across from the response side with a core coil being mounted on each of the fastening sides and both being attached to the same AC-DC transformer.
In accordance with further features of the present invention, the base housing or the main part may be provided with a dovetail extension pocket on a fastener side and a probe having, on each of one or two of the cube sides, a quadratic head undercut on all sides which may be slipped or inserted into the dovetail suspension pocket.
Advantageously, in accordance with the present invention, an open end of the dovetail suspension pocket may be closed off by a threaded pressure plate.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings which show, for the purpose of illustration only, several embodiments in accordance with the present invention.